Damp Proof Course Failure

Damp Proof Course Failure

Damp Proof Course Failure:


What causes damp proof course failure? There could be a number of reasons really. Many people are unaware that although they have a damp proof course (DPC) in place it can be breached and/or can fail.


DH Damp Proofing & Plastering are aware that many period properties across London and Berkshire were constructed without a damp proof course and these have later been retrospectively installed to protect the property from damp.  Properties that were constructed later generally have a DPC installed at the time they were built however the efficiency and longevity of these vary.


Early DPC’s were constructed merely from a layer of bitumen that was poured over the lowest course of the bricks and left to harden before the next course was laid. This method had a limited lifespan and the majority of DPC of this type have since failed. The bitumen failed as it was unable to cope with the expansion and contraction of the brickwork, developers changed their approach and instead coated a strip of hessian with bitumen and laid this on the bricks as this could cope with the expansion and contraction. Bitumen, although not the most effective damp proof course was in fact used for around 50 years meaning there are many properties that will have required a new DPC in recent years.


The next material that was used as a DPC was a tough material called pitch polymer. This material is well equipped to deal with the natural movement of the walls and although it did slide a little was much more effective than its predecessor. It is still possible though for a polymer damp proof course to fail due to its age.


The newest kid on the block is an injected damp proof course. This was firstly given a 10-year lifespan which has now increased to 25 years making it the longest lasting DPC. It is extremely rare for an injected DPC to fail due to its age. Problems have been encountered with this damp-proof course however this is usually down to the tradesmen installing it either attempting to cut corners or installing it incorrectly. People believe that this method of installing a DPC is the most effective as they were generally installed at the same time as central heating meaning that any damp affected plaster would have been removed during this time to gain access for the central heating systems.


Regardless of which type of damp proof course that you have within your property you should expect at some point to carry out either renewal or maintenance. The most important thing is to ensure your property does have a DPC in place and if you are purchasing a property that this has a DPC and if not one should be retrospectively installed.


The causes of a failed DPC vary. One situation that we see at DH Damp Proofing & Plastering is that the ground level on the exterior of the property is altered in some way allowing moisture to ingress above the DPC and causing problems on the interior. For example, before adding a driveway or a patio, discuss with your contractor the possibility of it breaching the DPC and decide what measures are to be put in place before the work starts, it may be the case that the ground level at that point will be higher than your DPC you should then seek a professional to install a new DPC at the correct level. Outside general maintenance can change the exterior ground level and cause water to flow towards your property above the level of your DPC.


Many people like to have foliage around their properties to improve the outward appearance. However, foliage can cause damp proof course failure especially climbing plants such as ivy as this grows up the property. As plants are an ideal surface for moisture to settle the close to your property it is the higher the chance the moisture from the plants will ingress into your home. The perfect solution here is to not have any climbing plants and if there are any cut them down before they cause a problem.


Trees that are close to your property also pose a risk. Their roots contain moisture along with the leaves at the top. The roots can make their way into the foundations of the property and breach the DPC. Any trees close to your property should be monitored and if not subject to conservation protection, removed.


If you are concerned about a breach or failure of your damp proof course we would advise you seek the opinion of a specialist who can check that you have one in place and that it is working effectively. A DPC installation or repair should never be attempted as a DIY project and should only ever be attempted by an experienced contractor.





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